In the casting of a metal strip of the type described at the outset, a layer of impurities and oxides floats to the surface of the molten metal bath between casting rolls. In addition, during the feed of the molten metal and the movement of the casting rolls, surface waves and surface streams in the melt result in an upward flotation of the liquid metal and a movement of the impurities onto the casting rolls. As a consequence, there is a danger that parts of the melt will be more intensively cooled on the cooled casting rolls and will prematurely solidify. In addition, the impurities and oxides flush onto the casting roll surfaces from the turbulent molten bath surface and are entrained by the casting rolls. This can create nonuniformities in the strip surface and reduce the strip quality.